2. Using radioactivity in dating Reviewing basic atomic structure Nucleus –Protons – positively charged particles with mass –Neutrons – neutral particles with mass –Electrons – negatively charged particles that orbit the nucleus

3. Using radioactivity in dating Reviewing basic atomic structure Atomic number –An elements identifying number –Equal to the number of protons in the atoms nucleus Mass number –Sum of the number of protons and neutrons in an atoms nucleus

4. Using radioactivity in dating Reviewing basic atomic structure Isotope –Variant of the same parent atom –Differs in the number of neutrons –Results in a different mass number than the parent atom

5. Using radioactivity in dating Radioactivity Spontaneous changes (decay) in the structure of atomic nuclei

6. Using radioactivity in dating Parent – an unstable radioactive isotope Daughter product – the isotopes resulting from the decay of a parent Half-life – the time required for one-half of the radioactive nuclei in a sample to decay

7. Absolute dating eg. Radiometric –The percentage of radioactive atoms that decay during one half-life is always the same (50 percent) –However, the actual number of atoms that decay continually decreases –Comparing the ratio of parent to daughter yields the age of the sample

8. Absolute dating eg. Radiometric –Comparing the ratio of parent to daughter yields the age of the sample

9. Using radioactivity in dating Radiometric dating Useful radioactive isotopes for providing radiometric ages –Rubidium-87 –Thorium-232 –Two isotopes of uranium –Potassium-40

11. Using radioactivity in dating Radiometric dating Sources of error –A closed system is required –To avoid potential problems, only fresh, unweathered rock samples should be used

12. Using radioactivity in dating Importance of radiometric dating Radiometric dating is a complex procedure that requires precise measurement Rocks from several localities have been dated at more than 3 billion years Confirms the idea that geologic time is immense